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Polars again

  1. Mar 30, 2008 #1
    1. The problem statement, all variables and given/known data

    A.Using polar coordinates, evaluate the improper integral of e^(-10(x^2+y^2))dxdy
    B. use part A to integrate from negative infinity to positive infinity of e^(-10x^2)dx

    2. Relevant equations[/b]

    3. The attempt at a solution

    i got part A to be pi/10, but for part B i clueless, can someone please give me a hit on how to integrate it!
  2. jcsd
  3. Mar 30, 2008 #2


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    pi/10 looks ok. But for the second part you aren't supposed to do another integration. You are supposed to realize the first integral can be split into the product of a dx integral and a dy integral both of which look the same. Use exp(-10(x^2+y^2))=exp(-10x^2)*exp(-10y^2).
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